Good news, as I love 5 Centimeters per Second (I'm uncertain whether or not I think it's better than YN). I do think it handled the themes Shinkai tries to convey in his work better and more candidly than YN. On the other hand YN is a better "movie" experience in the sense of being more fulfilling throughout. All in all, it's a definite buy for me.
Children Who Chase Lost Voices was a bit of let down. Not a bad movie as such, just that it tried to do something different from his previous (and subsequent) movies and didn't succeed. It's almost as if he heard that "next Miyazaki" epithet and took it literally. Bit uncertain if I buy this, but probably do for the sake of completeness as then I'd have every Shinkai movie.